Centrifugally cast pipe



Patented Aug. 3, 1937 7 2,088,663,: CENTRIFUGALLY cAs'r PIPE l CarLBardun, Gelsenkirchen, Germany, assignor to Centrifugal Pipe Corporation, Jersey City, N. J a corporation of Delaware No Drawing. Application December 12, 1936, Se-

rial No. 115,543. In Germany March 26, 1934 Claims.

This invention relates to centrifugal casting and particularly to pipe produced by the centrifugal casting method. This application is a continuation-impart of my copending application,

5 Serial Number 5,403, filed February 7, 1935, now Patent No. 2,068,244. The invention has for its object the production of pipe, the exterior layer or skin of which is enriched in phosphorus. Due to the high phosphorus content of the pipe ex- 10 terior, it is highly resistant to corrosive action, particularly to acids and acid soils. In producing the pipe of the invention, a centrifugal mold is lined or coated with a layer of phosphorus-bearing material, such as a compound or an alloy of phosphorus, preferably in pulverulent form, either alone or admixed. with another material, and molten metal is poured into the mold over the layer of material. When an alloy or compound is used, it should contain as its major constituents,

phosphorus and the metal to be cast.

Alloys of phosphorus with the basic material of the casting can be employed with particular advantage, for example, compositions containing ferro-phosphorus may be used as a lining on centrifugal molds for the casting of iron pipes, or a material containing copper phosphide may be I used in the production of copper pipes.

It is a particular object of the invention to produce cast iron pipe having an exterior shell or 0 skin that contains a relatively high percentage of phosphorus. In producing such pipe, any suitable iron, such as iron of the type customarily used in producing centrifugal pipe castings, is poured into a centrifugal mold lined with a layer of phosphorus-bearing material. For this purpose, I have found that it is desirable to use an alloy having a high phosphorus content and one that may readily be reduced to a pulverulent state, such as ferro-phosphorus.

40 The coating material should be ground to a fine state of subdivision so that it may readily be applied to the mold in a uniform layer of the desired thickness. For best results, the phosphorus-bearing material is applied to the mold in the form of a dry fine powder. In some cases, it has been found advisable to employ a binding medium in conjunction with the powdered phosphorus-bearing material, to facilitate adhesion to the wall of the mold.

do ing apparatus may be used, such as the dumptrough or retractible mold types. The pipe may I be produced in either refractory or sand-lined centrifugal molds, or in cooled metallic centrifugal 55 molds which are suitably lined with a phosphorus- Any of the present forms of centrifugal castbearing material. The phosphorus-bearing material may be applied by any suitable means that will produce a layer or coating of the desired uniformity and thickness. in the form of a loose, dry, powder may be applied to the mold during rotation by means now known in the art, such as a mechanical shaker or duster, or by means of a gas in which the powder is entrained. In view of the absorption of phosphorus by the iron, that quantity of coating composition should be use-d which will enrich the skin of the pipe in phosphorus the desired amount. The mold, accordingly, must be coated before each pipe is cast. When the molten iron is poured into the mold the phosphorusbearing material is burned or fused into the skin of the iron.

Favourable results may be obtained, for example, with a lining of ferro-phosphorus containing about 20-30% phosphorus and about 80-70% iron. The desired action of the applied form-phosphorus begins at a certain minimum amount which depends upon the casting material and the cross-section and wall-thickness of the articles to be cast. The lowest amount necessary for producing the desired effect may be determined in each particular case. It must, however, be noted that the resulting effect will be diminished if the form-phosphorus is used in amounts which are so large as to be completely absorbed by the casting material. The most favourable effect is The material, When highest amounts which still can be completely dissolved at the temperature and wall-thickness prevailing in each special case. Said maximum moreover depends upon its special composition and more particularly upon the melting-point thereof and its afiinity to the casting material. For instance, the favourable amount for a ferrophosphorus powder of the above-mentioned composition (20-30% phosphorus and 80-70% iron) amounts to between about 30-60-grms. per squaremeter of the surface of the mold to be lined, in the case of the manufacture of cast iron tubes of an average cross-section and of average wallthickness.

Copper phosphide, which can also be employed with advantage in the production of centrifugal castings of: non-ferrous metallic alloys, has been found to exert a like favourable effect.

I have found that objects cast centrifugally,

with one surface in contact with the mold'andthe other surface exposed to the air, such as passivity and power of resistance to the action of acids and like corrosive agents, in the, soil. r

I claim:

1; A centrifugally cast pipe having a, lower phosphorus content in the interior portion of the pipe wall than in the exterior portion of the pipe wall. 7

2. A centrifugally cast, cast iron pipe having that portion of the pipe wall which contacted the centrifugal mold, enriched in phosphorus.

3. A centrifugally cast, cast iron pipe having an exterior surface in which a phosphorus-bearing 'material was fused.

4. A centrifugally cast, cast iron pipe having an exterior surface in which an alloy of phosphorus was fused. V

5. A centrifugally cast pipe formedof ordinary cast iron, having the skin of the exterior portion thereof enriched in phosphorus.

CARL PARDUN. 

